Step-up converters (boost converters) have an inductive storage element, a switching element for the clocked application of an input voltage to the inductive storage element, and a rectifier arrangement which is connected to the inductive storage element. The rectifier arrangement has a diode as a proficient rectifier element and a capacitive storage element which provides an output voltage.
During operation of such a step-up converter, the switching element is turned on cyclically for a turned-on period. During this turned-on period, energy is stored in the inductive storage element and the inductive storage element is magnetized thereby. When the switching element has been turned off, this stored energy is output to the rectifier arrangement.
In one known method the magnetization state of the inductive storage element is monitored and the switching element is respectively turned on again as soon as the inductive storage element is completely demagnetized. During the turned-off period of the switching element, the switching element has a voltage across it which corresponds approximately to the output voltage of the step-up converter. If the switching element has a parasitic capacitance, this capacitance is charged to the output voltage during the turned-off period and is discharged when the switching element is turned on again. This process results in switching losses, which are greater the greater the parasitic capacitance of the switching element.